Joao Pinto, CMDT.LA, Instituto de Higiene e Medicina Tropical, Lisbon, Portugal
11 August 2010
In Methods: the sentence “This strain has a known microsatellite profile for the loci used that differs from the widespread dhfr triple mutant lineage of Asian origin (Roper C pers comm.)” should read “This strain has a known microsatellite profile for the loci used that matches the widespread dhfr triple mutant lineage of Asian origin (Roper C pers comm.)”
In Discussion: the sentence “This strain has a microsatellite profile that differs from the intercontinental widespread triple mutant haplotype of Southeast Asian origin (Roper C. pers. comm.)” should read “This strain has a microsatellite profile that matches the intercontinental widespread triple mutant haplotype of Southeast Asian origin (Roper C. pers. comm.)”
In the course of the analysis of the haplotype composition of dhfr triple mutants based on the allele profile of flanking microsatellite loci there was a misinterpretation that requires clarification. In previous studies a variety of marker loci have been used, sometimes the same loci with different primers, but invariably different sequencing machines. As a result the microsatellite alleles reported to be associated with the African dhfr triple mutant of Asian origin are not the same. For this reason African triple mutant alleles need to be run alongside Asian mutant controls using the same protocol and on the same sequencer. In our study two related microsatellite profiles were found, 108/183/210 (H4) and 114/183/210 (H5). The Southeast Asian P. falciparum laboratory K1 strain has a microsatellite profile that matches the widespread dhfr triple mutant with a shared origin between Africa and SE Asia and this was found to match the 114/183/210 (H5) haplotype. The confusion arose because of the similarity in size of the minor allele at the 0.3kb locus to that reported by Ndiaye et al. (2006) using extended primers (as in this study).
Therefore, the most frequent haplotype found in STP islands (H5) is more likely to represent the widespread African triple mutant with a shared SE Asian origin, as opposed to what is stated in the text. While this misinterpretation does not affect the discussion of our findings in terms of multiple introductions of dhfr triple mutants into the islands, this clarification will provide the reader with a correct interpretation of the data in a regional/continental context. It also highlights the potential problems of such comparisons due to the difficulties in standardizing and reproducing protocols in different laboratories.
A comparison between the dhfr triple mutant haplotypes observed in this study with the most similar haplotypes previously described can be found in the table available at http://www.ihmt.unl.pt/file/Erratum.pdf
ERRATUM
11 August 2010
In Methods: the sentence “This strain has a known microsatellite profile for the loci used that differs from the widespread dhfr triple mutant lineage of Asian origin (Roper C pers comm.)” should read “This strain has a known microsatellite profile for the loci used that matches the widespread dhfr triple mutant lineage of Asian origin (Roper C pers comm.)”
In Discussion: the sentence “This strain has a microsatellite profile that differs from the intercontinental widespread triple mutant haplotype of Southeast Asian origin (Roper C. pers. comm.)” should read “This strain has a microsatellite profile that matches the intercontinental widespread triple mutant haplotype of Southeast Asian origin (Roper C. pers. comm.)”
In the course of the analysis of the haplotype composition of dhfr triple mutants based on the allele profile of flanking microsatellite loci there was a misinterpretation that requires clarification. In previous studies a variety of marker loci have been used, sometimes the same loci with different primers, but invariably different sequencing machines. As a result the microsatellite alleles reported to be associated with the African dhfr triple mutant of Asian origin are not the same. For this reason African triple mutant alleles need to be run alongside Asian mutant controls using the same protocol and on the same sequencer. In our study two related microsatellite profiles were found, 108/183/210 (H4) and 114/183/210 (H5). The Southeast Asian P. falciparum laboratory K1 strain has a microsatellite profile that matches the widespread dhfr triple mutant with a shared origin between Africa and SE Asia and this was found to match the 114/183/210 (H5) haplotype. The confusion arose because of the similarity in size of the minor allele at the 0.3kb locus to that reported by Ndiaye et al. (2006) using extended primers (as in this study).
Therefore, the most frequent haplotype found in STP islands (H5) is more likely to represent the widespread African triple mutant with a shared SE Asian origin, as opposed to what is stated in the text. While this misinterpretation does not affect the discussion of our findings in terms of multiple introductions of dhfr triple mutants into the islands, this clarification will provide the reader with a correct interpretation of the data in a regional/continental context. It also highlights the potential problems of such comparisons due to the difficulties in standardizing and reproducing protocols in different laboratories.
A comparison between the dhfr triple mutant haplotypes observed in this study with the most similar haplotypes previously described can be found in the table available at http://www.ihmt.unl.pt/file/Erratum.pdf
Competing interests
None declared